//这里是调用 Windows API函数来进行截图

         //首先导入库文件

         [System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")]

         //声明函数

         private static extern IntPtr CreateDC

         (

             string Driver,   //驱动名称

             string Device,   //设备名称

             string Output,   //无用，可以设定为null

             IntPtr PrintData //任意的打印机数据

          );

         [System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")]

         private static extern bool BitBlt(

             IntPtr hdcDest,     //目标设备的句柄

             int XDest,          //目标对象的左上角X坐标

             int YDest,          //目标对象的左上角的Y坐标

             int Width,          //目标对象的宽度

             int Height,         //目标对象的高度

             IntPtr hdcScr,      //源设备的句柄

             int XScr,           //源设备的左上角X坐标

             int YScr,           //源设备的左上角Y坐标

             Int32 drRop         //光栅的操作值

             );

 private void button1_Click(object sender, EventArgs e)

         {

             //创建显示器的DC

             IntPtr dcScreen = CreateDC("DISPLAY", null, null, (IntPtr)null);

             //由一个指定设备的句柄创建一个新的Graphics对象

             Graphics g1 = Graphics.FromHdc(dcScreen);

             int tmpWidth, tmpHeigth;

             //获得保存图片的质量

             long level = long.Parse(this.textBox5.Text);

             //如果是全屏捕获

             if(this.radioButton1.Checked == true)

             {

                 tmpWidth = Screen.PrimaryScreen.Bounds.Width;

                 tmpHeigth = Screen.PrimaryScreen.Bounds.Height;

                 Image MyImage = new Bitmap(tmpWidth, tmpHeigth, g1);

                 //创建位图图形对象

                 Graphics g2 = Graphics.FromImage(MyImage);

                 //获得窗体的上下文设备

                 IntPtr dc1 = g1.GetHdc();

                 //获得位图文件的上下文设备

                 IntPtr dc2 = g2.GetHdc();

                 //写入到位图

                 BitBlt(dc2, , , tmpWidth, tmpHeigth, dc1, , , );

                 //释放窗体的上下文设备

                 g1.ReleaseHdc(dc1);

                 //释放位图的上下文设备

                 g2.ReleaseHdc(dc2);

                 //保存图像并显示

                 SaveImageWithQuality(MyImage,level);

                 this.pictureBox1.Image = MyImage;

             }

             else

             {

                 int X = Convert.ToInt32(this.textBox1.Text);

                 int Y = Convert.ToInt32(this.textBox2.Text);

                 int Width = Convert.ToInt32(this.textBox3.Text);

                 int Height = Convert.ToInt32(this.textBox4.Text);

                 Image Myimage = new Bitmap(Width, Height,g1);

                 Graphics g2 = Graphics.FromImage(Myimage);

                 IntPtr dc1 = g1.GetHdc();

                 IntPtr dc2 = g2.GetHdc();

                 BitBlt(dc2,,,Width,Height,dc1,X,Y,);

                 g1.ReleaseHdc(dc1);

                 g2.ReleaseHdc(dc2);

                 SaveImageWithQuality(Myimage, level);

                 this.pictureBox1.Image = Myimage;

             }

         }

  //保存图片时设置质量

         private void SaveImageWithQuality(Image bmp,long level)

         {

             ImageCodecInfo jgpEncoder = GetEncoder(ImageFormat.Jpeg);

             System.Drawing.Imaging.Encoder myEncoder =

                 System.Drawing.Imaging.Encoder.Quality;

             EncoderParameters myEncoderParameters = new EncoderParameters();

             EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, level);

             myEncoderParameters.Param[] = myEncoderParameter;

             bmp.Save(@"test.jpg", jgpEncoder, myEncoderParameters);

         }

         private ImageCodecInfo GetEncoder(ImageFormat format)

         {

             ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

             foreach (ImageCodecInfo codec in codecs)

             {

                 if (codec.FormatID == format.Guid)

                 {

                     return codec;

                 }

             }

             return null;

         }